Newly released recordings reveal 9/11 horror

New York: Audio of the stunned exchanges between ground control, pilots and authorities during the September 11, 2001 attacks on the US have been made public for the first time.

The tapes of the exchanges were published by the Rutgers Law Review overnight in the run-up to the 10th anniversary of the attacks.

"Did you just say something hit the World Trade Centre?" an incredulous military official asked shortly after the start of the attacks.

Minutes later, with air traffic authorities warning that another commercial jet was off course and just 10 kilometres from the White House, Washington ground control sounded in denial, saying it was "probably just a rumour".

Moments later, American Airlines Flight 77 slammed into the Pentagon.

The recordings illustrate just how unprepared the United States was for the audacious plot.

While portions of the audio have circulated before, the document published by the review allows an unprecedented, blow-by-blow recreation of the brief period on September 11, 2001, when four airliners were hijacked and slammed into New York, the Pentagon and a Pennsylvania field.

The raw recordings released in the run-up to the 10th anniversary of the tragedy show air controllers desperately trying to understand what happened to the planes, where they were, and where they were going.

In one exchange, a controller at New York Centre says there were reports of a fire at the Twin Towers.

"And that`s the area where we lost the airplane," the controller said.

At the same time, an unidentified pilot is asking over the airwaves: "Anybody know what that smoke is in lower Manhattan?"

At Boston Centre control, a worker says: "We have a problem here, we have a hijacked aircraft headed towards New York and ...we need someone to scramble some F-16s or something up there to help us out."

The answer, revealing the astonishment at what was happening, is: "Is this real world or exercise?"

Even at 8:43, a full 19 minutes after suspected American Airlines Flight 11 hijacker Mohamed Atta broadcast to air traffic control that "We have some planes," and nine minutes after Boston Centre notified controllers of the flight`s hijacking, Major James Fox, leader of the Northeast Air Defence Sector who is patched in to the breaking developments, expressed disbelief.

"I`ve never seen so much real-world stuff happen during an exercise," Major Fox said, according to the transcript.

As millions of Americans tuning in to news broadcasts watched the second jet hitting the World Trade Centre, New York air traffic controllers sounded dumbfounded at the events.

"Another one just hit the building," a controller said.

New York Centre: "Wow."

New York Terminal Radar Approach Control (TRACON): "Oh my God."

New York Centre: "Another one just hit the World Trade."

New York TRACON: "The whole building just came apart...oh my God."

New York Centre: "Holy smokes. All right, I guess you guys are going to be busy."

At 9:38 am, 35 minutes after the second plane hit the Twin Towers, controllers in Washington sounded sceptical about hijacked Flight 77 bearing down on the US capital.

When asked whether they knew anything about controller reports that a rogue jet was near the White House, Washington Centre responded: "No, we do not and it`s probably just a rumour.”

"But you might want to call National (airport) or Andrews somebody (Andrews Air Force base), somewhere like that and find out, but we don`t (know) anything about that."

The recordings, which also include tragic exchanges with flight attendants on Flight 11 about how two of their colleagues had been knifed and hijackers were in the cockpit, were first reported by The New York Times.

The 9/11 Commission tasked Rutgers Law Review with piecing together the critical communications of that morning, and the Review said in its preface "the raw material that went into our reconstruction of the day was not obtained easily".

"If we had not pushed as hard as we did - ultimately persuading the commission to use its subpoena power to obtain the records - many of the critical conversations from that morning may have been lost to history," it said.